Minerals and Metals in Ancient India v1.c18.s4.t2: Copper Slag and Artefacts from Rājghāṭ
Minerals and Metals in Ancient India v1.c18.s4.t2
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Copper Slag and Artefacts from Rājghāṭ
v1.c18.s4.t2.1
Analysis of the Rājghāṭ copper slag showed that it was chiefly iron silicate with 5.39 per cent calcium oxide, whereas the Ahar slag did not contain any calcium oxide. Evidently, lime was used as a flux, a new innovation in India, and this is also shown in the CaO content (1-2.5 %) in the copper artefacts of Rajghat. (Bhardwaj, 1979) Presence of 1 per cent + copper oxide in the metallic phase shows that the molten copper was not properly ‘green poled’ or dexoidised.
v1.c18.s4.t2.2
Metallographic examination showed that the copper sheet of Rājghāṭ had globular alternate banding of Cu-CuO eutectic. Annealing twins provided the evidence of heat-treatment having been done. Bronze coins had segregated Cu-rich Zone and Sn-rich grain boundary, proving that it was a cast structure. Very good coining and embossing were revealed in some Pre-Christian era Taxila coins which had glassy elongated slag streaks and fine equi-axed grains; these were evidently hot-worked, then cold-worked, and finally annealed. (Bhardwaj, 1979: 81)